ARCA biopharma, Inc. (Nasdaq: ABIO), a biopharmaceutical company developing genetically-targeted therapies for atrial fibrillation, heart failure and other cardiovascular diseases, today provided an update on a proposed, genetically-targeted clinical trial in atrial fibrillation (“AF”) of the Company’s lead developmental drug, Gencaro (bucindolol hydrochloride). The Company also announced that Medtronic, Inc., a leader in medical technologies to improve the treatment of chronic diseases, including cardiac rhythm disorders, has signed a non-binding Letter of Intent to collaborate on the initial, Phase 2B portion of the proposed trial. The Proposed GENETIC-AF Phase 3 Adaptive Design Clinical Trial The trial, known as GENETIC-AF, is projected to be a 620-patient, Phase 3 study comparing Gencaro to metoprolol CR/XL for prevention of AF in patients with heart failure and left ventricular dysfunction ("HFREF"). The Trial is planned to be genetically enriched by enrolling only those patients who possess the cardiac beta-1 adrenergic receptor genotype 389 arginine homozygous, which in the Beta Blocker Evaluation of Survival Trial ("BEST") was associated with an enhanced response to Gencaro in preventing atrial fibrillation. The Company estimates that this genotype is present in about 50% of the U.S. population. The primary endpoint of GENETIC-AF is planned to be the combination endpoint of recurrent symptomatic AF and all-cause mortality, over 24 weeks post electrical cardioversion for persistent AF. Commencement of the GENETIC-AF is conditional on receipt of the necessary funding, which ARCA intends to secure through equity financing or a strategic partnership. ARCA has created an adaptive design for GENETIC-AF, under which the Company plans to initiate a Phase 2B study in approximately 200 HFREF patients. Depending on the results of the Phase 2B portion, the trial could then be expanded to a Phase 3 study by enrolling an estimated additional 420 patients. A secondary endpoint of the proposed Phase 2B portion of the trial will be AF burden, defined as a patient’s actual time in AF, regardless of symptoms. Under the Company’s proposed design, all 200 patients in the Phase 2B portion of the trial will have AF burden measured by continuous monitoring, either by previously implanted cardiac resynchronization or defibrillation devices, or newly or previously inserted implantable loop recorders . At the end of enrollment of the first 200 patients, the primary endpoint of recurrent symptomatic AF and all-cause mortality, and the secondary endpoint of AF burden will be evaluated by the trial’s Data and Safety Monitoring Board for evidence of an efficacy signal. If a sufficient efficacy signal is detected and acceptable safety is observed, the trial would then proceed to the Phase 3 portion and full enrollment. ARCA believes that Gencaro has potential as a treatment for AF, based on placebo-controlled data from the Phase 3 heart failure BEST study. A retrospective analysis of data from the BEST Trial shows that patients with the genotype that ARCA plans to enroll in GENETIC-AF had a 74% reduction in the risk of AF compared to placebo (p = 0.0003). These same patients experienced a 38% reduction in the risk of all cause mortality (p < 0.05) and statistically significant improvements on other major clinical efficacy endpoints.